Systems For Sealing and Venting a Manhole

ABSTRACT

A manhole cover system (10) for sealing manholes to minimize water infiltration includes a manhole cover (12) re-movably inserted into a manhole cover frame (14) having a compressible gasket (28) attached thereto. Manhole cover (12) includes a base (16) and a peripheral rim (18). Peripheral rim (18) includes a cover outer peripheral surface (20) and a horizontal cover seat (22). Manhole cover frame (14) includes a frame cover restraint wall (24) and a frame seat (26). During assembly, peripheral rim (18) is removably seated on frame seat (26) of manhole cover frame (14). Compressible gasket (28) forms a seal within a vertical clearance space (32) between cover outer peripheral surface (20) and frame cover restraint wall (24).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. provisional application 62/430,418, filed Dec. 6, 2016, U.S. provisional application 62/470,937, filed Mar. 14, 2017, and U.S. provisional application 62/512,439, filed May 30, 2017, and U.S. provisional application 62/522,385, filed Jun. 20, 2017, the entire contents of each application being incorporated by reference herein.

FIELD

The subject technology relates generally to manhole covers and specifically to systems and methods for sealing and ventilating manholes, to minimize unwanted water infiltration, and for inducing air flow, including gasket systems.

BACKGROUND AND SUMMARY

The subject technology is useful for underground vaults, manholes, conduits, boats, or any other structure where sealing to minimize water infiltration (e.g. rain water) and/or ventilation is important. In some aspects, the subject technology can be utilized in both new construction and in retrofit applications. In one aspect, the subject technology is utilized with sanitary sewer manholes. However, the subject technology is not limited to this application.

A manhole is a relatively large-diameter, generally vertical pipe made of brick or a series of pre-cast concrete sections that extend downwardly to underground pipes or tunnels. Typically, a large cast-iron frame with a removable cast iron cover is installed on the upper portion, or chimney section, of the manhole to provide an access by maintenance personnel. The covers and the chimneys can become sources of water infiltration into the manhole.

Manholes for sanitary sewers are located in streets, roadways, ditch lines, yards and many other areas that are prone to flooding conditions. A study in 1976 was conducted by the Neenah Foundry Company titled “Report of Inflow of Surface Water through Manhole Covers” that describes in detail problems with rain water entering the sewer system through the cover. Unwanted water infiltration significantly burdens sanitary sewer collection system capacity, pump capacity, wastewater treatment plant capacity, and causes sanitary sewer overflows to the environment and public waterways. Today, many types of manhole covers are sealed, which prevents air from flowing into and out of the sewer system. However, venting or ventilation of sealed covers is oftentimes necessary, for instance, to mitigate sewer gas buildup in the manhole.

Sealing Manhole Covers Against Water Infiltration

Manhole covers typically leak significant amounts of rain or surface water and oftentimes lie in flood-prone areas. There is a problem created by the clearance space between the cover's outer peripheral and the frame as rain water and debris can enter the manhole through the clearance space. It is therefore desirable to seal against such intrusion. There have been numerous attempts with various systems and methods employed to seal the clearance space between the sewer manhole frame horizontal seat and cover horizontal seat area, such as gaskets, bolt down lid with gaskets, or inserted plastic or metal dishes to minimize the inflow of water through the lid. All such designs are dependent upon the weight of the cover on the frame seat. However, if the frame seat area is not clean upon setting of the cover, water will still flow in between the cover and frame seat.

Horizontal gaskets are sometimes used but they are ineffective. If debris is present between the horizontal seats the sealing action is compromised. Even a small pebble wedged between the gasket and manhole cover can cause 20 gallons per minute of leakage when the manhole is submersed by only a ¼ inch of water. Known sealing systems experience problems that occur due to road traffic. The starting and stopping of traffic rotates the lid, and thus the gaskets. Accumulated debris will tear or wear down the gasket, thus allowing water to enter the sanitary sewer system.

Even if existing horizontal seats worked properly, the vertical annular space between the cover and frame invites standing water after rainfall. Debris builds up in this annular space upon evaporation of the water, which causes corrosion between the two surfaces which makes the cover extremely difficult to remove. Typically, this is not the case due to the fact the horizontal seat leaks rain water and carries debris into the horizontal seat area and into the sanitary sewer collection system.

Some known sealing systems utilize loosely secured gaskets recessed into the cover seat that can become easily lost when removing or installing the cover by dragging the cover across the frame. The cast iron manhole cover is frequently dragged instead of lifted because of its heavy weight.

There remains a need for a relatively simple and economical manhole cover sealing system. In one aspect, the manhole cover system provides for sealing a portion of the vertical clearance space between the cover and frame with a seal including a compressible gasket (tapered in one aspect), which can also be covered by silicone or other coating to reduce friction. Such a vertically oriented gasket is superior because it can block debris because of its vertical position. Additional advantages are realized because the vertical force exerted by the cover does not wear out the vertical seal whereas conventional horizontal seals are eventually compromised by the weight of the cover and further exacerbated by additional forces such as automobiles driving over them. Furthermore, the silicone coating material provides chemical resistance, a smooth, slippery surface and is water resistant to ensure simple and easy cover installation and removal. The gasket is secured onto the frame vertical wall. The silicone grease material is applied to the underside of the gasket (adjacent to the frame seat) and onto the outer (exposed) surface of the gasket. The seal is installed in two pieces connected with a butt type joint which effectively covers the entire periphery of the manhole.

In another aspect, the present manhole cover system provides for sealing a portion of the vertical clearance space between the cover and frame with a seal including a tapered compressible foam gasket covered by a smooth-surfaced tape ring. The system can shed debris because of its vertical position and is configured such that no dead weight load from the cover is directly applied to the seal itself, and the seal materials have a relatively longer life span. Furthermore, the tape ring material provides chemical resistance and a smooth, slippery surface to ensure simple and easy cover installation and removal.

A manhole cover system for sealing the vertical annular clearance space between a round manhole casting frame and cover is disclosed in one aspect of the subject technology. The cover includes a cover seat and cover outer peripheral surface that matingly fit onto to a frame seat and within the frame cover restraint wall of the frame. The cover outer peripheral surface and frame cover restraint wall are configured with a 5 to 10 degree angle with respect to the vertical axis for ease of installation. Providing a tapered fit allows the cover to fit firmly inside the frame. The sealing area is located within the first clearance space disposed between the cover outer peripheral surface and the frame cover restraint wall. The system includes a flexible, tapered, compressible foam gasket covered by a smooth-surfaced tape ring in one aspect. The foam gasket is secured onto the frame vertical wall, corner of the frame cover restraint wall and a portion of the frame seat. The tape ring is adhered to the foam gasket, thus enabling it to be free floating relative to the frame. The tape ring is installed in two pieces with an overlapping joint onto the adjoining tape ring located 180 degrees apart in one aspect. The tape ring is the wearing surface when the cover is installed and forms a compressive seal due to the compressive nature of the foam gasket. The tape ring and foam gasket are tapered downwardly from the vertical top position to enhance the ease of the cover installation. A small portion of the foam gasket extends beyond the tape ring at both the top and bottom to secure the tape ring, to keep debris out from behind the tape ring and to restrain the tape ring. The system is configured such that the full load from the weight of the cover does not bear or rest against the tape ring or foam gasket. When the cover is installed the cover engages the tape ring, and deforms and compresses the foam gasket into the frame cover restraint wall. The two sections of the tape ring that are free floating on the foam gasket and overlapped to form the seal against the cover vertical surface. The foam gasket and tape ring thus provide a consistent sealing surface area when installed around the entire perimeter of the inside of the frame cover restraint wall.

In some aspects, the manhole cover sealing systems presented herein are more effective at preventing infiltration of water overall when used in combination with a manhole cover design that has no vent holes and has a recessed pick hole or similar feature for removing the cover (in lieu of a pick hole). Such a system provides a substantially water-tight, long lasting manhole cover sealing system that reduces rain/inflow into the sanitary sewer system.

Sealing Manhole Chimneys Against Water Infiltration

Manhole chimneys can also be a source of water infiltration into a manhole. The chimney is the upper portion of the manhole which can be constructed of brick or solid concrete riser rings, and which is adjusted in height to meet final grade requirements. Bonding the chimney and frame together to make a water-tight seal is difficult due to surface load (i.e., traffic loads) and freezing/thawing conditions on both the manhole frame and chimney area. Furthermore, it can be difficult to achieve and maintain an acceptable seal between the frame and the chimney, since the frame and the chimney are typically made of differing materials and thus expand and contract at different rates. Also, the chimney section constructed of brick or precast concrete rings can deteriorate over time due to load and freeze/thaw conditions.

Typically, the joint between the chimney and frame is sealed by being mortared together. However, once installed, the mortared seals and the chimney bricks or riser rings can be a significant source of unwanted inflow and infiltration of ground water into the sewer system. There are a number of known methods for sealing the cast iron frame to the manhole chimney wherein a seal is installed on external portions of the manhole chimney and frame. However, installation and repair of such external seals usually requires removal and reinstallation of the frame. In addition, such systems are problematic in that the seals provide limited flexibility to conform to the contour of the pipe. Additionally, bonding to the pipe is both costly and labor-intensive to install. In contrast, the subject technology is relatively simple and economical to install.

There remains a need for an effective system and method for sealing the interior portion of a masonry manhole or conduit structure. The system includes a flexible seal having one or more liners, a water-activated adhesive sealant, the sealant being positioned intermediate the seal and the manhole interior surface, and water applied in a specific manner to activate the sealant so as to form an expanding sealing mixture. The seal is configured for fastening adjacent to a masonry chimney of the manhole or conduit, and for spanning a joint between the chimney and a metal frame of the manhole. Optionally, foam members may be added to adsorb and retain more sealant at specific points in the subject area if needed where offsets occur in the masonry surface. Fasteners may be used, such as those used with power nailing, to attach the one or more liners to the masonry chimney wall or conduit at various points. The expanding sealing mixture is urged into the voids and joints of the masonry chimney or conduit. A lip seal may be added to one or more edges of the liners to minimize/contain the sealant from flowing beyond the area covered by the liners.

Venting of Manhole Covers

Today, more and more efforts are placed on preventing rain water from entering sanitary sewer systems. In the past, covers were vented by virtue of pick holes for removing the cover; which allowed air to flow into and out of the manhole and to the pipes below. Today, manhole covers are oftentimes sealed against water which incidentally prevents air from flowing into and out of the sewer system. However, ventilation is oftentimes necessary, for instance, to mitigate gas buildup.

Hydrogen sulfide is created by organic matter typically found in oxygen-depleted sanitary sewer systems. This in turn, when combined with moisture, forms sulfuric acid which degrades the concrete/masonry material in both the pipes and manholes causing significant long term damage. Consequently, a sewer system requires a fresh air source to maintain sufficient oxygen levels to inhibit the formation of hydrogen sulfide.

All that is required is 1 mg/liter of dissolved oxygen in the water to stop the formation of hydrogen sulfide. Air enters conventional sanitary sewer system through roof vents at high elevations and typically manhole covers at the lower elevations creating a steady air flow pattern. However, this does not occur with sealed manhole covers. Providing a system and method of enabling ventilation while also sealing from unwanted water (e.g. rain) infiltration has many different applications and benefits.

There are a number of known venting systems used today designed to keep rain water out of the manhole system. However, most known systems require an elevated vent to keep rain water out. There can be a problem during flooding as the elevated vent does not keep water out when the water depth exceeds the height of the raised vent, nor does it address snow plows hitting the raised vent. Known systems are both costly and labor-intensive to install. In contrast, in one aspect, the subject technology is a venting system that does not use a raised vent, includes an automatic valve that is economical, relatively simple to install, and can be installed in flat covers.

In one aspect, the venting system includes a valve body; a vent screen threadedly securable to a top portion of the valve body; the vent screen having vent holes; the vent screen being bonded to a first end of a memory foam component (e.g. hydrophilic open cell memory foam material); the memory foam component having foam vents aligned with the vent holes; a valve bonded to a second end of the memory foam component; and a valve seat formed in an opening in a bottom portion of the valve body; the valve seat being adapted to cooperatively fit the valve; the memory foam component being capable expanding from an open position to a closed position upon becoming substantially saturated with water.

In dry conditions, air flows through vent openings in the vent screen, through the foam material and out the vent opening located on the bottom. Air can flow in either direction. When rain or elevated water occurs, the water enters in through the vent screen and into the foam. Because the foam material is hydrophilic, it absorbs the water. The foam material is adhered to and suspended in the vertical position from the vent screen. The foam gains the weight of the water and stretches or elongates thus the valve lowers and rests within the valve seat shutting off the water flow. Additional water depth increases the compression of the valve into the valve seat, thus stopping all water flow into the structure.

After the rain event (or other flooding condition), the water evaporates and is enhanced by the wicking capabilities of the foam to bring the moisture to the surface of the vent screen. After sufficient water has evaporated, the memory foam retracts or contracts, raising the valve from the valve seat, thus allowing air to flow through the foam and enhancing the evaporation process.

The vent screen is screwed into the top of the valve body and flanged section. The vent screen, foam and valve are all combined by adhesive as one part. The entire part can be removed from the top of the cover for maintenance and inspection purposes. It can easily be replaced as needed. The vent screen and foam can be cleaned by a simple vacuum cleaner. In addition, the unit can be tested for operational ability by placing a low pressure vacuum system and measuring the vacuum generated.

Domed Manhole Cover

In an alternative aspect, a manhole cover system includes a dome-shaped manhole cover removably inserted into a manhole cover frame. The dome-shaped manhole cover includes a single aperture disposed entirely through the cover located at approximately the apex of the dome shape; the manhole cover includes a cover seat and a cover outer peripheral surface.

The dome-shaped manhole cover is adapted to fit the manhole cover frame. The manhole cover frame includes a frame seat and a frame cover restraint wall. In some aspects, a compressible gasket is attached to the frame cover restraint wall wherein the manhole cover is removably seated on the frame seat of the manhole cover frame such that the compressible gasket forms a seal between the outer peripheral surface of the manhole cover and the frame cover restraint wall. The domed manhole cover can be used by itself or alternatively with the various venting and sealing systems described herein. The dome shape allows the aperture (aka vent) to be vertically higher so as to minimize water infiltration.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the inventive aspects will become apparent to those skilled in the art to which the aspects relate from reading the specification and claims with reference to the accompanying drawings, in which:

FIG. 1 is a section view of a system for sealing a manhole frame and manhole cover showing a manhole cover elevated above for clarity, according to an aspect of the subject technology;

FIG. 2 is an enlarged section view of the system in FIG. 1 shown with no cover and the compressible gasket of the sealing system being in the uncompressed state;

FIG. 3 is an enlarged section view of the system in FIG. 1 shown with the cover seated and the compressible gasket of the sealing system being in the compressed state;

FIG. 4 is a sectional view of the seal and gasket as shown in FIG. 1, depicted with grease on the exposed surfaces;

FIG. 5 is a plan view of the ends of the sections of compressible gasket attached with a butt joint;

FIG. 6 is an enlarged view of the frame seat and frame cover restraint wall with typical vertical angle, the figure being shown with a manhole cover removed for clarity;

FIG. 7 is an enlarged section view of the compressible gasket of FIG. 1;

FIG. 8 is a section view of a system for sealing a manhole frame and manhole cover showing a manhole cover elevated above for clarity, according to another aspect of the subject technology;

FIG. 9 is an enlarged section view of the system in FIG. 8 shown with no cover and the compressible gasket of the sealing system being in the uncompressed state;

FIG. 10 is an enlarged section view of the system in FIG. 8 shown with the cover seated and the compressible gasket of the sealing system being in the compressed state;

FIG. 11 is a further enlargement of the seal and gasket as shown in FIG. 9;

FIG. 12 is a plan view of the ends of the sections of compressible gasket and tape ring overlap attached with a butt joint;

FIG. 13 is a top plan view showing the installation of a first liner of a system for sealing a manhole chimney according to an aspect of the subject technology, the figure being shown with a manhole cover removed for clarity;

FIG. 14 is a top plan view showing the installation of a second liner of the system of FIG. 13;

FIG. 15 is a view in section of the system installation of FIG. 13 and additionally showing a removable manhole cover;

FIG. 16 is a partial expanded view in section showing details of the lip seal of FIG. 15;

FIG. 17 is a partial expanded view in section showing details of the system installation of FIG. 13

FIG. 18 is a partial expanded view in section of FIG. 17 showing the first liner pulled out to allow more sealant to be added;

FIGS. 19 and 20 are a flow diagram showing the steps of a method for sealing a manhole chimney or conduit according to an aspect of the subject technology;

FIG. 21 is a section view showing the installation of a system for a manhole cover per an aspect of the subject technology, the figure being shown with a manhole cover in the dry status with valve in the open position;

FIG. 22 is a section view of the system installation as in FIG. 21 filled with water and the valve in the closed position;

FIG. 23 is a plan view on top of a manhole cover showing the vent holes and flange;

FIG. 24 is a sectional view of a manhole cover system for sealing and venting a manhole frame and cover according to an aspect of the subject technology;

FIG. 24A is an enlarged sectional view of a part of FIG. 24; and

FIG. 25 is a perspective cutaway view of a manhole cover and manhole cover frame, in one aspect.

DETAILED DESCRIPTION

In the discussion that follows, like reference numerals are used to refer to like structures and elements in the various figures.

The general arrangement of the installation of a manhole cover system 10 (“system 10”) for sealing a manhole cover and manhole frame is shown in FIGS. 1 through 7 per various aspects of the subject technology. As depicted in FIG. 1, system 10 includes a manhole cover 12 removably inserted into a manhole cover frame 14. Manhole cover 12 includes a base 16 and a peripheral rim 18. Peripheral rim 18 includes a generally vertical cover outer peripheral surface 20 (“cover outer peripheral surface 20”) and a generally horizontal cover seat 22.

Manhole cover 12 is adapted to fit manhole cover frame 14. Manhole cover frame 14 includes a frame cover restraint wall 24 and a frame seat 26. During assembly, peripheral rim 18 is removably seated on frame seat 26 of manhole cover frame 14. Cover outer peripheral surface 20 and cover seat 22 are configured to matingly fit manhole cover frame 14, with cover outer peripheral surface 20 being adjacent to frame cover restraint wall 24 and with cover seat 22 being adjacent to frame seat 26.

Referring to FIGS. 2 and 3, in one aspect, a compressible gasket 28 is attached to frame cover restraint wall 24 by an adhesive 30. Peripheral rim 18 of manhole cover 12 is removably seated on frame seat 26 of manhole cover frame 14 such that compressible gasket 28 forms a seal within a vertical clearance space 32 between cover outer peripheral surface 20 of manhole cover 12 and frame cover restraint wall 24. In an alternative aspect, compressible gasket 28 is attached to cover outer peripheral surface 20 of manhole cover 12 by adhesive 30, to form a seal within vertical clearance space 32.

In one aspect, system 10 includes a sealing system 34. Sealing system 34 further includes a coating 36 applied to an outer surface 38 and bottom surface 40 of attached compressible gasket 28. Sealing system 34 reduces rainwater infiltration into the manhole by forming a seal at vertical clearance space 32. The seal is formed as compressible gasket 28 is compressed from an initial, uncompressed state 42 (FIG. 2) to a compressed state 44 (FIG. 3) by the seating of manhole cover 12.

In one aspect (e.g. FIG. 7), compressible gasket 28 includes a void area 46 disposed generally centrally inside the interior of the compressible gasket. In one aspect, compressible gasket 28 has a generally triangular cross sectional profile and void area 46 is shaped as a triangular cutout in the middle thereof. In one aspect, compressible gasket 28 further includes a dimple or bend groove 48 disposed in a horizontal portion 50 below void area 46. Void area 46 and bend groove 48 facilitate the upward and inward folding (or flexing) of horizontal portion 50 as compressible gasket 28 is compressed from uncompressed state 42 to compressed state 44 during the seating of manhole cover 12.

Referring to FIG. 3 and FIG. 6, in some aspects, cover outer peripheral surface 20 and corresponding frame cover restraint wall 24 are configured typically at a 5 to 10-degree taper angle 52 with respect to a vertical axis. This tapering facilitates ease of assembly for manhole cover 12 to fit firmly inside of manhole cover frame 14.

When manhole cover 12 is seated inside manhole cover frame 14, vertical clearance space 32 has a horizontal distance measured between cover outer peripheral surface 20 and the inside of frame cover restraint wall 24 of from about 0.25 inch to about 0.375 inches. Also, the vertical distance measured between the cover seat 22 and frame seat 26 should be close to about zero inches when no debris is present. However, when manhole cover 12 is removed from manhole cover frame 14, small particulates of debris can enter and become settled against frame seat 26. When manhole cover 12 is re-seated inside manhole cover frame 14 this layer of debris creates a horizontal seat clearance space between cover seat 22 and frame seat 26. This horizontal seat clearance space provides a pathway for water to enter the manhole. Any water entering through an unsealed vertical clearance space 32 can then flow through the horizontal seat clearance space into the manhole, and into the sewer system. This water infiltration is problematic, as described elsewhere herein. Sealing system 34 mitigates this problem.

Positioning sealing system 34 in the vertical clearance space 32 provides a seal to reduce water infiltration even when debris is present. This benefit is further enhanced by the application of coating 36 (a layer of water-resistant silicone grease in one aspect) having low friction design properties. Installing a non-metallic sealing system 34 (in one aspect) in the vertical clearance space 32 also reduces corrosion issues between the two metal surfaces (the cover outer peripheral surface 20 and the frame cover restraint wall 24).

Prior to installation of sealing system 34, the surface area of manhole cover frame 14 is cleaned to ensure proper adhesion. The metal surface can be prepared by any suitable method, including wire abrasion or sand blasting, for example. After cleaning, compressible gasket 28 is attached to frame cover restraint wall 24 by adhesive 30 to firmly fix it to the manhole cover frame 14.

Compressible gasket 28 can be produced in a continuous type roll that would enable the installer to cut pieces to length as required for each application and size of manhole cover frame 14. The overall depth/height of sealing system 34 can vary depending on the depth/height of the frame cover restraint wall 24 utilized. Sealing system 34 can be installed in two sections, a first section 54 and a second section 56, with both sections of compressible gasket 28 being connected at their ends with a butt joint 58, as seen in FIG. 5. Approximately equal lengths of compressible gasket 28 for first section 54 and second section 56 are measured and cut as required to cover the entire inside circumference of frame cover restraint wall 24. Additional sections may be utilized depending on the size of the circumference of the frame cover restraint wall 24 to be sealed. Utilizing a plurality of sections provides for greater ease of installation of adhesive 30 and compressible gasket 28 by ensuring continuous coverage around the circumference with no gaps. It should be noted that a single piece of gasket material having two ends can be used which requires only one butt joint. Additionally, a unitary piece of pre-formed material can be used which is appropriately sized and thus requires no butt joint.

Referring again to FIG. 2, compressible gasket 28 has a generally triangular shape and includes a generally flat inner surface 60 configured for attachment to frame cover restraint wall 24 via adhesive 30. Once attached, the triangular shape of compressible gasket 28 results in bottom surface 40 being positioned at about a 20 degree angle relative to frame seat 26. This angle provides a pocket 62 between bottom surface 40 and frame seat 26 configured to receive coating 36. Coating 36 is then applied to outer surface 38 and bottom surface 40 of attached compressible gasket 28. When sealing system 34 is fully assembled after connection of butt joints 58, it covers about 60 to 75 percent of the depth/height of cover outer peripheral surface 20 with a compressible seal.

System 10 is configured such that the full load from the weight of manhole cover 12 does not bear or rest against sealing system 34. As seen in FIGS. 2-4, during installation, the top end 64 of compressible gasket 28 is positioned vertically at approximately 25 percent below the top of the frame cover restraint wall 24. This positioning of top end 64 enables manhole cover 12 to be seated by initially falling onto and engaging frame cover restraint wall 24. This engagement sequence acts to reduce damaging or displacing sealing system 34. During seating, manhole cover 12 engages, deforms, and compresses compressible gasket 28 radially onto frame cover restraint wall 24, which provides a consistent compressive seal around the entire perimeter of the frame cover restraint wall. When manhole cover 12 is fully installed, its full weight rests on the frame seat 26.

Referring to FIGS. 2 and 3, outer surface 38 of compressible gasket 28 is curved in order to guide the manhole cover 12 as it falls, allowing it to slide into place inside manhole cover frame 14, and thereby enhancing centering of the manhole cover 12 onto frame seat 26. The curved outer surface 38 provides a smooth, angled surface for manhole cover 12 to abut as it falls into position, centering itself within frame seat 26. During seating, engagement of cover outer peripheral surface 20 against outer surface 38 also wipes off of any debris that may be on the cover outer peripheral surface, thus minimizing debris falling onto frame seat 26. Seating engagement of manhole cover 12 provides radial pressure against compressible gasket 28 to form a compressive seal around the complete cover outer peripheral surface 20. Coating 36 further promotes movement of compressible gasket 28 when the compressible gasket is in transition from uncompressed state 42 to compressed state 44, and minimizes debris buildup.

FIG. 7 is an enlarged section view of one aspect of compressible gasket 28. As shown, compressible gasket 28 is in the generally angled orientation as it would be when attached to frame cover restraint wall 24 of manhole cover frame 14. As shown, inner surface 60 is oriented at approximately 7.5 degrees relative to a vertical axis. The outer surface 38 of compressible gasket 28 has a generally curved shape (a radius of about 2.462 inches in one aspect). Bend groove 48 of horizontal portion 50 has a radius of about 0.010 inches in one aspect. Compressible gasket 28 is flexible and compressible and fabricated to the shape as shown in FIGS. 4 & 7.

In one aspect, compressible gasket 28 is made from EPDM (ethylene propylene diene monomer) rubber or other suitable elastomeric material. In another aspect, Nitrol is used. In one aspect, adhesive 30 is made from a high-strength, high-solids, low-VOC polyurethane adhesive, (i.e. 3M 5200 marine adhesive and sealant, or MasterWeld 948, available from BASF Construction Chemicals of Beachwood, Ohio), or other suitable adhesive configured for firmly bonding a rubber gasket to a cast iron frame. In one aspect, coating 36 is made from silicone grease (i.e. Dow Corning 111 Valve Lubricant and Sealant) or other suitable water-resistant lubricant having low friction design properties.

The general arrangement of the installation of a manhole cover system 100 (“system 100”) for sealing a manhole cover and manhole frame is shown in FIGS. 8 through 12 according to another aspect of the subject technology. As depicted in FIG. 8, system 100 includes manhole cover 12 removably inserted into manhole cover frame 14, and a sealing system 134. Similar to system 10, cover outer peripheral surface 20 and corresponding frame cover restraint wall 24 of system 100 are configured typically at a 5 to 10-degree taper angle 52 with respect to a vertical axis. This tapering facilitates ease of assembly for manhole cover 12 to fit firmly inside of manhole cover frame 14.

Referring to FIGS. 9 and 10, in one aspect, sealing system 134 includes a compressible gasket 128 having a tape ring 136, the compressible gasket being attached to both frame cover restraint wall 24 and frame seat 26 by an adhesive 130 (similar in application to adhesive 30). Prior to the installation of sealing system 134, the surface area is cleaned and prepared to ensure proper adhesion, similar to system 10. Compressible gasket 128 with tape ring 136 attached may be installed in a position inside manhole cover frame 14 similar to compressible gasket 28, as described above. Peripheral rim 18 of manhole cover 12 is removably seated on frame seat 26 of manhole cover frame 14 such that sealing system 134 forms a seal within vertical clearance space 32 between cover outer peripheral surface 20 of manhole cover 12 and frame cover restraint wall 24. Sealing system 134 acts to substantially prevent rainwater infiltration into the manhole through vertical clearance space 32.

Compressible gasket 128 is preferably made from flexible, compressible, closed cell foam. Closed cell type foam material minimizes water retention in the gasket material. In one aspect, compressible gasket 128 is fabricated into the somewhat triangular shape as shown in FIGS. 9 and 11, for installation in an initial, uncompressed state 42. Tape ring 136 is attached to compressible gasket 128 by adhesive or alternatively is laminated to it. This allows tape ring 136 to move/shift upon flexible compressible gasket 128 during seating of manhole cover 12.

As best seen in FIGS. 9 and 11, compressible gasket 128 includes a first foam extension 138 and a second foam extension 140, the extensions configured to extend beyond the placement of tape ring 136. The first and second extensions 138, 140 act to prevent debris from getting underneath the tape ring 136 and to constrain the movement of the tape ring. First foam extension 138 extends vertically from a top end 142 of compressible gasket 128 and second foam extension 140 extends horizontally from a bottom end 144 of the compressible gasket.

Tape ring 136 is preferably made from Ultra High Molecular Weight Polyethylene (UHMW) plastic material. As compared to other plastic materials, UHMW has increased abrasion resistance, higher tensile strength, higher impact resistance, increased chemical resistance, and a smoother, more slippery surface. The slippery, low friction interior surface of tape ring 136 assists in shedding debris that may enter the manhole when manhole cover 12 is removed. UHMW is also easily machined and can withstand the range of temperatures typically encountered in various applications of the subject technology. Similar to sealing system 34, sealing system 134 provides a non-metallic seal in vertical clearance space 32 that reduces corrosion issues between the two metal surfaces, the cover outer peripheral surface 20 and frame cover restraint wall 24. Furthermore, the UMHW material provides the desired level of flexibility needed for tape ring 136. The flexibility allows tape ring 136 to deform in and out along with compressible gasket 128 when compressed by peripheral rim 18 of manhole cover 12.

The smooth, slippery surface on the interior side of tape ring 136 allows manhole cover 12 to rotate normally under vehicular traffic conditions. Also, the slippery surface characteristics of tape ring 136 allows for easier removal of manhole cover 12 because the tape ring resists bonding or adhesion to the cover outer peripheral surface 20. Furthermore, as described above, the smooth, slippery surface of tape ring 136 allows debris to fall off the inner surface of the tape ring and onto frame seat 26. Even small amounts of debris lodged in vertical clearance space 32 can provide a channel to enable rainwater to flow into the manhole and into the sanitary sewer. Utilizing the vertical seal method minimizes rainwater reaching the horizontal surface of frame seat 26

As best seen in FIG. 11, compressible gasket 128 includes a generally flat inner surface 146, an outer surface 148, and a generally flat bottom surface 150. Compressible gasket 128 is attached to manhole cover frame 14 by adhesive 130 engaging inner surface 146 and bottom surface 150 of the compressible gasket. Inner surface 146 is made to be at an angle of approximately 7.5 degrees relative to a vertical axis. This angle allows inner surface 146 to matingly attach to frame cover restraint wall 24 simultaneously as bottom surface 150 is matingly attached to frame seat 26. Outer surface 148 includes a radius surface or tapered portion 152 proximate top end 142. Tapered portion 152 acts as a guide to enable the cover outer peripheral surface 20 and cover seat 22 to fall by gravity into manhole cover frame 214 without damaging sealing system 134. Further, as manhole cover 12 is seated, tapered portion 152 wipes off any debris that may be on cover outer peripheral surface 20, thus minimizing debris reaching frame seat 26.

Similar to compressible gasket 28, compressible gasket 128 with tape ring 136 attached to outer surface 148 may be produced in a continuous type roll, that would enable the installer to cut to length pieces as required for each application and size of manhole cover frame 14. Sealing system 134 may be installed in two sections, a first section 154 and a second section 156, joined at butt joints 158, and with overlapping tape ring joints 160, as seen in FIG. 12. The installer would cut to length a first section 154 and a second section 156 as required to cover half of the frame inside circumference plus an overlap of about 0.375 to 0.5 inches. The installer would remove the portion of the compressible gasket 128 from the overlap tape ring joints 160 section area to allow only the ends of tape ring 136 to overlap the adjacent section of the sealing system 134. The ends of compressible gasket 128 would abut to the adjacent section of the compressible gasket at butt joint 158. There are at a minimum at least two overlapping tape ring joints 160 and butt joints 158 per sealing system 134. Additional sections may be required dependent upon the overall inside circumference to seal. Overlap tape ring joints 160 allow tape ring 136 to move freely upon compressible gasket 128 when manhole cover 12 is installed and allows for temperature expansion and contraction of the tape ring.

Depending on the degree of taper angle 52 of frame cover restraint wall 24, which can vary slightly, the end of the section of compressible gasket 128 with tape ring 136 attached will need to be cut on an angle. Such angle will ensure that compressible gasket 128 abuts the entire depth/height of the seal at the adjoining first and second seal section(s) 154 & 156. Utilizing a plurality of sections provides for greater ease of installation of adhesive 130 and compressible gasket 128 by ensuring continuous coverage around the circumference of frame cover restraint wall 24 with no gaps.

Similar to System 10, system 100 is configured such that the full load from the weight of manhole cover 12 does not bear or rest against sealing system 134. During seating of manhole cover 12, cover outer peripheral surface 20 engages tape ring 136, and compresses compressible gasket 128 radially onto frame cover restraint wall 24, which provides a consistent compressive seal around the entire perimeter of the frame cover restraint wall. When manhole cover 12 is fully installed, its full weight rests on the frame seat 26, and compressible gasket 128 is in compressed state 44 (see FIG. 10).

The general arrangement of the installation of a system 200 for sealing a manhole chimney or conduit is shown in FIGS. 13 through 18 according to an aspect of the subject technology. System 200 includes a first liner 212 extending between a manhole cover frame 214 and a chimney 216, the first liner for sealing together the manhole cover frame and the chimney. A sealant/adhesive (hereafter generally termed “sealant”) 218 is intermediate first liner 212 and manhole cover frame 214. Sealant 218 is likewise intermediate first liner 212 and chimney 216.

First liner 212 is preferably a semi-rigid, flexible sheet material that can easily be bent into shape or alternatively heated to allow formation into specific shapes to fit a given application. First liner 212 may be made from any suitable material including, but not limited to, plastic, or natural or synthetic rubber. The preferred liner material is a plastic, such as a polycarbonate material that does not split when power-nailed onto the manhole wall. The liner material may be heated and shaped or molded into irregular shapes, and has sufficient strength to withstand low pressure hydrostatic pressures. In some aspects, first liner 212 may include structural reinforcing, such as a plurality of ribs, for example.

Preferably, an interior side 220 of first liner 212 is smooth and an opposite, exterior side 222 of the first liner facing the chimney 216 and sealant 218 is textured to improve adhesive qualities for the sealant to bond to. The flexibility of first liner 212 allows it to be installed over various offsets in the masonry surface of chimney 216. First liner 212 operates to both contain the sealant 218, directing the sealant expansion by urging it into the voids and joints of a masonry interior surface 224, and to act as the final stop to deter water from entering the manhole or conduit structure. Once installed, first liner 212 allows for an increased amount of sealant 218 to be applied without excessive sealant material flowing outside the area to be sealed. It is beneficial to minimize the gap between first liner 212 and chimney 216 to be sealed to maximize the sealant 218 expansive qualities to flow into the voids and joints of the masonry interior surface 224.

Manhole cover frame 214 is typically made from metal, such as cast or machined iron or steel, and includes an opening 226 therethrough, the opening being covered by a lid or manhole cover 228 that is received by a receptacle portion 230 of the manhole cover frame. When manhole cover 228 is coupled to manhole cover frame 214, the manhole cover closes off access to a manhole 232 beneath manhole cover frame 214 and chimney 216.

Chimney 216 is a generally vertical structure made from a masonry material such as concrete, but may be formed of other materials, such as bricks. Chimney 216 forms a generally hollow support foundation which includes an opening 234 therethrough. Manhole cover frame 214 is attached to the top of chimney 216. Although chimney 216 is shown with a circular cross section, it may have other suitable shapes, such as oval, square or rectangular. Further, although system 200 is shown in an application for sealing a vertical chimney to a metal frame, system 200 may also be used to seal connecting joints or cracks in horizontal conduit or piping sections.

Sealant 218 is preferably a grout comprising water-activated polyurethane flexible foam having both moisture-sealing and adhesive properties, though any suitable type of sealant and/or adhesive may be used within the scope of the subject technology. Those of skill in the art will appreciate the expansive nature of sealant 218. The grout material is viscous, but may be pumped and spray applied. When activated with water, sealant 218 becomes a sealing mixture 236, and may expand up to ten times its original volume. The grout's adhesive qualities allow sealant 218/sealing mixture 236 to bond to the masonry interior surface 224 of chimney 216, to the textured first liner 212 and to the manhole cover frame 214.

Once water is added, the reaction rate of sealing mixture 236 may be from about ten minutes to about two hours, depending upon temperature and ratio of water to sealant. Maintaining a ratio of two to five parts water to one part sealant 218 is preferred. Typically, using a ratio of two parts water to one part sealant 218 provides less expansion, but has better adhesion. Using a ratio of five parts water to one part sealant 218 provides more expansion, but has reduced strength and adhesion, comparatively. After installation, the sealing mixture 236 backed up with first liner 212 may withstand hydrostatic pressures in excess of 15 psi. Sealing mixture 236 performs as a primary water proofing seal for manhole 232, and the combination of first liner 212 on one side joined with a second liner 238 on the opposite side form a completed annular seal 240 which acts as a secondary seal for the manhole.

Adjoining sheet panels of first liner 212 and second liner 238 may be overlapped and power nailed together or connected via an H channel, or other suitable connector to make seal 240. Although power nailing using a suitable fastener, such as a nail 242 with a washer 244 is shown, first liner 212 and second liner 238 may be fastened to masonry interior surface 224 by any suitable fastener or connector, such as screws, pins or anchors. Seal 240 thus extends around and adjacent to the inner circumference of manhole 232, and is secured in place by power nailing into the masonry interior surface 224 of chimney 216. Although seal 240 is shown with first liner 212 and second liner 238, seal 240 may include one or more liners.

A lip seal 246 may be added to the bottom end or any edge of seal 240 to further contain the sealing mixture 236 from expanding/flowing beyond the area covered by the seal. Lip seal 246 may be an elongated strip made of any suitable flexible, water-proof material, such as, without limitation, rubber or plastic. Lip seal 246 is generally “L” shaped, and configured to attach by friction-fit at one end to the bottom end of first liner 212 and engage masonry interior surface 224 at the opposite end.

Active water leaks into manhole 232, (distinguished from mere water seepage) must be stopped prior to installing system 200. If active leaks are present, the pressure from the water infiltration can wash the applied sealant 218 away from the desired area of manhole 232 being sealed. Active leaks at manhole 232 may be sealed using the same sealant 218 described above. Sealant 218 may be injected directly into the masonry structure leaking point and also into the surrounding soil outside of the structure to stop active water leaks.

In some manhole applications there may be portions of chimney 216 where significant masonry off-sets occur that would generally require an additional thickness of sealant 218 to allow for optimum engagement with seal 240. In such applications it is preferred to add optional foam members 248 to those specific offset areas to support the additional sealant 218 needed. Foam members 248 may be made of any suitable synthetic porous material, such as, but not limited to, spun polypropylene fiber pads. The viscous sealant 218 adheres to foam members 248 to enable higher concentrations of the sealant be applied to those specific areas with minimal sealant flowing by gravity down the wall. Foam members 248 may be attached to the masonry wall by power nailing, or by any suitable fasteners or connectors.

To achieve optimum results, seal 240 needs to fit as closely to the masonry surface as possible. The center of seal 240 is to be compressed toward the masonry surface by a press 250. Press 250 may be any suitable press, such as, without limitation, a hydraulic, pneumatic, or mechanical press. With the center of seal 240 held firmly in place by press 250, the outer ends of seal 240 may then be power nailed to the masonry structure.

In one aspect, press 250 is pneumatically powered, manually operated (via toggle switch operatively connected to a pressurized air source), and further having two knee joints on opposing ends of two telescoping arms for engaging liners, 212, 238 and/or interior surface 224 of chimney 216 (or conduit). Although preferred, press 250 can be replaced by manually applying pressure.

Once seal 240 is installed or partially installed, additional sealant 218 may be added by injection either through a hole drilled through the seal or by injecting the sealant at the upper edge of the seal. The user may use one or more liner sections, and preferably two, opposing first and second liners, 212, 238, respectively, joined together at each of their adjoining side ends by a vertical seam 252.

It should be noted that the system and method of the subject technology, in the various forms described herein, can be implemented in applications other than chimneys and conduits without departing from the spirit of the subject technology; e.g. piping system, or a basement wall. Those of skill in the art will appreciate that such alternative aspects might necessitate varying uses, or non-use, of press 250.

In many cases, the process does not require manned entry into the structure to implement the system and method of the subject technology. In such cases a user, situated outside of the manhole (or other opening), can reach into the manhole to perform the installation (e.g. the chimney is to be sealed), including insertion and activation of press 250. On the other hand, there are other situations that require manned entry (e.g. implementing the subject technology below the chimney such as on a joint).

A method s100 for sealing a manhole 232 is shown in FIGS. 19, 20 according to an aspect of the subject technology. At s102 the portions to be sealed of masonry interior surface 224 of chimney 216 and an interior surface 254 of manhole cover frame 214 (working area 256) are cleaned by high pressure washer to remove loose material, rust, grease, etc. Cleaning working area 256 assists to ensure proper adhesion of sealant 218 to the masonry chimney 216 and manhole cover frame 214 for manhole 232. Residual moisture in chimney 216 from pressure washing may be utilized as detailed below to activate and ensure bonding of sealant 218.

At s104 an acid etching material may be spray applied to working area 256 to further clean and enhance the ability of sealant 218 to adhere to chimney 216 and manhole cover frame 214. The acid etching material may be any suitable acid such as, without limitation, muriatic acid (also known as hydrochloric acid), phosphoric acid or sulfamic acid. The acid etching material is rinsed off with water after about five to ten minutes.

Where large voids exist due to structural offsets or irregular shapes in masonry interior surface 224, at step s106 foam members 248 may be attached to the specific area(s) to allow additional sealant 218 to be applied at specific points without concern of the sealant flowing down the masonry wall. Foam members 248 may be power nailed with fasteners nail 242 and washer 244 to masonry interior surface 224.

At s108 sealant 218 is spray-applied into voids and joints and, optionally, onto foam members 248. The application of sealant 218 is performed in workable sections to minimize the sealant from dripping or flowing outside working area 256. For example, in a vertical manhole 232, the user may first divide the interior into two vertical halves, a first half 258 and a second half 260, for planning placement of first liner 212 and second liner 238. Next, the user may begin spray application of sealant 218 on the bottom one-third section of first half 258, which may be about 12 inches to about 18 inches in height, for example. The user would spray apply only enough sealant 218 to fill this workable section so to minimize runoff sealant from flowing down the vertical wall. Then, for example, work would continue in the next round with the middle one-third section of first half 258, followed by the top one-third section of first half 258. Second half 260 would then follow the same upward sequence, with workable sections being sealed from the bottom to the top.

At s110 first liner 212 and second liner 238 are cut to the desired size and shape to cover the working area 256 of manhole 232 in need of repair. The sizes of the liner pieces are cut to take into account the type of a vertical seam 252; whether the vertical seam is overlapping or abutting with a joint connector. First liner 212 is then positioned onto the subject area (first half 258).

At s111 press 250 may be utilized to apply pressure to the center and bottom portion of first liner 212, compressing to make a tighter fit of the first liner against masonry interior surface 224.

With press 250 in place, at s112 first liner 212 is attached to the masonry interior surface 224 by power nailing near the bottom end of the first liner. First liner 212 is installed to cover one half or more of the circumference of working area 256, while allowing for an overlap area at seam 252 for adjacent second liner 238 or abutting the second liner and joining by a connector. Once the bottom end of first liner 212 is secured, press 250 is removed for reuse.

At s113 the adjoining sections of liner, such as second liner 238 are installed similarly to first liner 212 by repeating steps s110 through s112. Once first liner 212 and second liner 238 are installed, the first and second liners can be manually deflected at s114 by pulling away (toward the interior of manhole 232) at the top end and applying more sealant 218 into the working area if desired. The fundamental purpose of first and second liners 212, 238 is to contain sealant 218 and make a final water stop barrier.

At s116 water is added to sealant 218 behind first liner 212 and second liner 238. Sealant 218 is activated by the moisture, becoming sealing mixture 236. Sealing mixture 236 then foams and expands, thus the contained sealing mixture expands into the concrete, voids, joints sections and performs the sealing process. Sealing mixture 236 adheres and bonds to both masonry interior surface 224 of chimney 216, interior surface 254 of manhole cover frame 214 (where applicable), and to first liner 212.

At s118, as installation continues progressing up the wall interior surface, additional sections of first liner 212 may be added for the next upper workable area. The bottom section may be overlapped by the added upper section, or alternatively the top of the lower section can be pulled outwardly and the bottom of the upper section can be inserted behind it in which case the bottom section overlaps the upper section. Then steps s108 through s114 may be repeated for the next workable area.

At s120 (water having been added at s116) tapping against first liner 212 and second liner 238 helps to move additional water into contact with sealant 218 to improve utilization of the sealant and its expansion rate as sealing mixture 236.

At s122, the adjacent side ends at vertical seams 252 of first liner 212 and second liner 238 may be joined by overlapping or abutting with a connector at seam 252. Then the side ends of second liner 238 may be power nailed adjacent to seam 252, completing seal 240.

At s124, additional sealant 218 may be added where needed by drilling a hole in seal 240 and injecting the sealant through the hole toward masonry interior surface 224 or by deflecting the top end of seal 240 and injecting the sealant from above. Additional water may then be added through either the hole or via the top end of seal 240.

The application may be used in both vertical and horizontal positions, with both flat surfaces and curved surfaces, for the purposes of water proofing concrete structures from low pressure water leakage. The thickness and overall strength of seal 240 and the number and locations of attachment points to the masonry interior surface 224 using nails 242 is dependent upon the maximum hydrostatic pressure applicable for that specific project. Seal 240 may be hand molded or heat utilized to shape the seal to specific shapes to fit different applications/surfaces. System 200 may also be used in conjunction with different manhole cover system aspects. For example, system 200 may be used with manhole cover systems 10 or 100.

As depicted in FIGS. 21-23, in one aspect, a venting system 300 for a manhole cover 312 includes a vented valve assembly 302 removably attached to a valve body 304. Vented valve assembly 302 includes a vent screen 306, memory foam component 308, and valve 310. Memory foam component 308 is attached at a top end to vent screen 306 and at a bottom end to valve 310. The attachment may be made with adhesive or other suitable fastening means. Valve 310 moves from an open position (FIG. 21) to a closed position (FIG. 22), sealing against valve body 304.

Vented valve assembly 302 also includes a plurality of hollow, substantially vertical fluid pathways 314 which allow air, moisture and water to flow between the exterior ambient environment and memory foam component 308. Fluid pathways 314 may be formed by drilling bore holes through vent screen 306, and partially into the memory foam component, or by other methods to achieve the same structural relationship. Each fluid pathway 314 includes an exclusive vent hole 316 (i.e. one fluid pathway per hole) passing through vent screen 306 aligned with a foam vent 318 disposed at the top end of memory foam component 308. Fluid pathways 314 are configured to minimize the amount of dirt and debris entering system 300.

As depicted in FIG. 21, system 300 is attached to manhole cover 312 or any such ceiling structure at an opening 320. In one aspect, system 300 includes a threaded locking collar 322 and gasket 324 for securing vented valve assembly 302 within opening 320. Valve body 304 includes a valve body flange 326 and flange threads 328. Valve body flange 326 is formed near a top portion of valve body 304, and is configured to extend outward, overlap, and engage the top edge of opening 320 in manhole cover 312. Flange threads 328 are disposed on the top of the interior sidewall of valve body 304 and are configured for threaded engagement with corresponding screen threads 330 disposed on the outer perimeter of vent screen 306. Other suitable means of removable engagement of vent screen 306 to valve body 304 are possible, including friction fitting.

Valve body threads 332 are disposed on the exterior sidewall of valve body 304 and are configured for threaded engagement with corresponding inner threads 334 disposed on threaded locking collar 322. Gasket 324 is configured for placement intermediate threaded locking collar 322 and manhole cover 312. During assembly of system 300 to the manhole, valve body 304 is first inserted into opening 320 until valve body flange 326 engages manhole cover 312. Then gasket 324 is aligned with threaded locking collar 322, and the threaded locking collar is screwed onto valve body 304, engaging gasket 324 against the bottom of manhole cover 312.

After system 300 is installed in opening 320, valve body flange 326, threaded locking collar 322 and gasket 324 act to substantially prevent water infiltration at opening 320 in manhole cover 312. Vent screen 306 is easily removed (unscrewed in one aspect) with a spanning wrench having two protrusions that cooperatively fit into at least two vent holes 316, thus permitting the vent screen, and thus vented valve assembly 302, to be rotated and threaded/unthreaded into/out of the valve body 304.

In one aspect, memory foam 308 has the following characteristics: open cell foam (to allow ease of both air and water flow), hydrophilic (water adsorbing), anti-microbial (minimize bacterial growth to maintain flow characteristics), wicking capabilities (enable the water moisture to raise to the vent screen 306 to enhance evaporation), chemically resistant for the design intended environment, capable of performing at various temperatures above freezing, does not degrade if frozen in water, flexibility (to enable stretching or vertical elongation due to the weight of the adsorbed water to close the valve 310), and a relatively high number of pores per inch (PPI) to enhance both air and water flow.

The proper cross flow of air/water through memory foam component 308 allows venting system 300 to both seal to minimize water infiltration and to vent to reduce buildup of sewer gas in the manhole. The flow pressure loss across the memory foam component 308 must be maintained low. Typically, the air pressure difference between the air space above and below venting system 300 is relatively small. Thus, the net air flow rate, or air exchange rate, is relatively low.

Referring again to FIGS. 21 and 22, the bottom end of valve body 304 includes a cylindrical valve opening 336 having a chamfered edge configured as a valve seat 338. Valve opening 336 is in fluid communication with the manhole below to allow for venting of sewer gas. In one aspect, valve 310 is shaped like a spherical segment (aka spherical cap). Valve seat 338 is shaped to cooperatively receive and engage valve 310 in a substantially watertight manner when in the closed position (FIG. 22).

FIG. 21 depicts valve 310 in an open (aka dry) position wherein air flows through vent holes 316 and foam vents 318 of fluid pathways 314, memory foam component 308, and through valve opening 336. As shown in FIGS. 21 and 22, vent screen 306 and valve body flange 326 are made in a slight arcuate, or dome-shape to shed water and to resist water accumulation. However, in certain high water or flooding conditions, water can enter and flow through vent holes 316 and foam vents 318 of fluid pathways 314, into memory foam component 308. The water causes memory foam component 308 to expand and stretch downward toward valve opening 336 as it becomes saturated. This expansion condition causes valve 310 to seat within valve seat 338, thereby closing off valve opening 336 to prevent unwanted water leakage into the manhole below (FIG. 22).

After cessation of the high water condition, water within fluid pathways 314 will evaporate, thereby opening the fluid pathways to allow for ambient airflow and moisture removal. Evaporation of water in memory foam component 308 occurs as moisture laden vapor exits through foam vents 318 and vent holes 316. As the water evaporates, memory foam component 308 contracts, retracts upward, and returns to the open (dry) position as valve 310 unseats from valve seat 338. Once valve 310 is back in the open position, sewer gas can vent again through valve opening 336.

As shown in FIGS. 21 and 22, in one aspect, the sidewall of memory foam component 308 is made with a tapered profile relative to the interior sidewall of valve body 304. The tapered profile minimizes any adherence of memory foam component 308 to the interior sidewall of valve body 304 and improves air flow characteristics. The vertical distance of valve 310 from valve seat 338 is relatively small in the open (or dry) position. The total travel distance between the dry state and wet state of valve 310 is relatively small, the approximate proportions being shown in FIG. 21. Those of skill in the art will appreciate that the subject technology can be sized commensurate with various applications.

Valve body 304, locking collar 322, valve 310, vent screen 306 and valve body flange 326 are constructed of durable corrosion resistant and moisture resistant material, such as plastics. Venting system 300 may be used in conjunction with different manhole cover system aspects. For example, venting system 300 may be used with manhole cover systems 10 or 100.

As depicted in FIGS. 24, 24A and 25, in one aspect, a manhole cover system 400 (“system 400”) includes a dome-shaped manhole cover 412 removably inserted into a manhole cover frame 414. Manhole cover 412 includes a domed base 416 and a peripheral rim 418. Peripheral rim 418 includes a generally vertical cover outer peripheral surface 420 (“cover outer peripheral surface 420”) and a generally horizontal cover seat 422.

Manhole cover 412 is adapted to fit manhole cover frame 414. Manhole cover frame 414 includes a frame cover restraint wall 424 and a frame seat 426. During assembly, peripheral rim 418 is removably seated on frame seat 426 of manhole cover frame 414. Outer peripheral surface 420 and cover seat 422 are configured to matingly fit manhole cover frame 414, with outer peripheral surface 420 being adjacent to frame cover restraint wall 424 and with cover seat 422 being adjacent to frame seat 426.

Domed base 416 includes a single aperture 425 disposed approximately at an apex 427, configured to provide an elevated vent through the domed base of manhole cover 412. In one aspect, the vertical height from the bottom of domed base 416 to apex 427 is about 4 inches. Those of skill in the art will appreciate that this dimension can be varied according to various anticipated water levels.

Although manhole cover 412 is shown as a circular-shaped cover having a curved, domed base, alternative square or rectangular covers may also be used which are configured with an elevated apex vent. Such alternative covers may include domed bases with four angled flat or curved portions.

In one aspect (FIG. 24A), a compressible gasket 428 is attached to frame cover restraint wall 424. Manhole cover 412 is removably seated on frame seat 426 of the manhole cover frame 414 such that compressible gasket 428 forms a seal between cover outer peripheral surface 420 of manhole cover 412 and frame cover restraint wall 424. Other aspects of the sealing function may be realized by utilization of sealing systems 34 or 134 as described above.

Similar to manhole cover systems 10 and 100, in some aspects, cover outer peripheral surface 420 and corresponding frame cover restraint wall 424 are configured typically at a 5 to 10-degree taper angle 52 with respect to a vertical axis. This tapering facilitates ease of assembly for manhole cover 412 to fit firmly inside of manhole cover frame 414.

As depicted in FIG. 24, manhole cover frame 414 is generally embedded into, and flush with ground surface 430. In an excess water, or flooding condition, ventilation is provided via aperture 425, and no leakage occurs into the aperture so long as water level 432 is below apex 427.

In another aspect, aperture 425 can be fitted with a venting system, such as described herein, including a valve to selectively close under certain conditions and act as a vent under other conditions. For example, manhole cover system 400 may be configured to utilize a venting system similar to venting system 300 as described above. In one aspect, an extension pipe can be added to extend the vertical height of the aperture. In one aspect, the aperture can be plugged (e.g. during extreme flooding conditions). In one aspect, the aperture can be used as a “pick hole” to facilitate removal of the manhole cover using a pickaxe.

While this invention has been shown and described with respect to detailed aspects thereof, it will be understood by those skilled in the art that changes in form and detail thereof may be made without departing from the scope of the claims of the invention. 

1. (canceled)
 2. A manhole cover system comprising: a manhole cover having: a cover seat, and an outer peripheral surface; a manhole cover frame having: a frame seat, a frame cover restraint wall, a compressible gasket having an outer surface and an inner surface that is attached to either the frame cover restraint wall of the manhole cover frame, or the outer peripheral surface of the manhole cover; wherein the outer surface of the compressible gasket has a tapered portion disposed proximate a top end of the of the gasket; wherein the manhole cover is removably seated on the frame seat of the manhole cover frame such that the compressible gasket forms a seal between the outer peripheral surface of the manhole cover and the frame cover restraint wall; wherein the outer surface of the compressible gasket is covered by silicone or other coating to reduce friction; wherein the compressible gasket includes a triangularly shaped void area disposed generally centrally inside the interior of the compressible gasket; wherein the compressible gasket includes a horizontal portion disposed below the triangularly shaped void area.
 3. The manhole cover system of claim 2 further comprising: the compressible gasket includes a dimpled portion disposed in a bottom surface of the compressible gasket, for allowing the horizontal portion to flex upwardly when the gasket is compressed. 